The present invention is directed generally to the field of collecting and drying samples of body fluid such as blood. The preferred embodiments are devices for collecting and drying capillary or venous blood samples for the subsequent analytical, quantitative determination of clinical chemistry analytes.
Methods for assaying the constituents of blood are indispensable tools in the diagnosis and treatment of human disease. Analysis of dried blood is advantageous as the blood sample can be self-collected, and shipment of the blood sample to the laboratory is simplified since storage at ambient temperature and shipping through regular mail is permitted. Analysis of dried blood is further advantageous in that the sample poses a reduced risk of biohazardous exposure and the sample remaining after initial analysis can be stored in a repository for later use.
It is well known in the art that blood may be collected and dried on absorbent material for subsequent clinical assays. For example, it is well known that blood can be collected and dried on Schleicher and Schuell no. 903(trademark) specimen collection paper and assayed for the presence of glycosylated hemoglobin (Little et al., xe2x80x9cCollection of Blood on Filter Paper for Measurement of Glycated Hemoglobin by Affinity Chromatographyxe2x80x9d, Clin. Chem. 32: 869-871 (1986); Little et al., xe2x80x9cMeasurement of Glycosylated Whole-Blood Protein for Assessing Glucose Control in Diabetes: Collection and Storage of Capillary Blood on Filter Paperxe2x80x9d, Clin. Chem. 30, 213-216 (1985)). Wet blood has also been collected and dried on Schleicher and Schuell no. 903(trademark) paper and then assayed for the presence of prostate-specific antigen (PSA) (Hoffman et al., xe2x80x9cassay of prostate-specific antigen from blood spotted on filter paper and application to prostate cancer screeningxe2x80x9d, Clin. Chem. 42, 536-544 (1996)).
Another absorbent material that has been used to collect wet blood is described in U.S. Pat. No. 5,563,042, xe2x80x9cWhole Blood Glucose Test Strip.xe2x80x9d The blood however was not dried and was assayed in its wet form for the presence of glucose (U.S. Pat. No. 5,563,042, supra).
One problem with collecting and drying blood is that the spots are not always uniform in the disbursement of whole blood/serum/whole blood cell components throughout the total volume of the matrix, leading to inconsistencies in analysis. One significant advantage of the present invention is that it allows for the collection and drying of blood samples that are of uniform volume and integrity. As a result, the analytical results are more accurate and reproducible.
Another advantage of the present invention is that once the blood sample is inside the apparatus there is a diminished risk of contamination or loss of integrity of the sample.
These and other objects of the invention will be apparent in light of the detailed description below.
The present invention relates to a device for consistently collecting and drying capillary or venous blood samples of a uniform quantity and integrity. The devices described below include a housing that defines an external opening, an internal compartment, and a channel interconnecting the opening and the compartment. The compartment is bounded at least in part by porous hydrophobic sheet material and encloses absorbent material. The sheet material allows water vapor to pass while retaining liquids. The absorbent material contained in the internal compartment optionally extends into the channel. A body fluid such as blood is applied through the external opening in the housing and is then drawn into the absorbent material in the internal compartment via the channel. Once the absorbent material in the internal compartment is saturated with fluid, then no more fluid will be drawn in to the device as the capillary action of the material will cease. The water- and air-vapor permeable nature of the sheet material allows fluid to dry in the housing without disassembling the device. After the fluid sample has dried, the device is disassembled and the sample or part of the sample is analyzed for the presence of a fluid constituent. The facile nature of operating this device permits even a user untrained in the blood collection arts to prepare a defined sample size of dried body fluid such as blood for laboratory analysis. As a result, the assay results are reproducible and consistent.
These and other features and advantages of the present invention may be better understood by considering the following detailed description of certain preferred embodiments of the invention. In the course of this description, reference will be made to the attached drawings.